Bio161 exam2 notes 6 PDF

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Bio161 Exam 2 lecture notes...

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Local potentials can be excitatory or inhibitory •

True- excitatory graded potential is going to be more positive, and more likely to trigger an !

Inhibitory potential is going to make membrane potential more negative, less likely to trigger an It is more likely to find chemical-gated channels in the membrane of an axon com[ared to a dendrite •

False- because chemical gated channels are going to be the channels that when they open up thats what triggers a local or graded potential!

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Local or graded potentials occur in the dendrites and cell body of a neuron whereas on the axon thats where the occurs!

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NO CHEMICAL GATED CHANNELS ON THE AXON OF A NEURON!

A strong excitatory stimulus will result in a larger depolarization of the cell membrane compared to weak excitatory stimulus •

True- graded/local potentials strength is relative to the strength of the stimulus!

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Depolarization- membrane potential is getting closer to zero, stronger excitatory stimulus= more depolarization!

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More channels open= stronger stimulus!

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Strong enough stimulus and graded potential reaches threshold value is triggered!

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Some stimuli are inhibitory- potassium (positively charged ions) leaves the cell OR chloride ions (negatively charged and adds the negative to the membrane potential) entering the cell---- THIS CAUSES HYPERPOLARIZATION! ◦

Because the membrane potential becomes more negative!

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Makes it less likely for the neuron to fire an !

If this type of neuron binds to GABA, what is the result? (hint what ion is diffusing and how will it change the charge inside the cell)

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The cell will hyperpolarize- chloride chemically graded channel, high outside low inside!

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Gaba is the chemical that opens the gate, chloride will flow in, they are negative, membrane potential becomes more negative. ICF is more negative compared to ECF!

If a person has a mutated GABA receptors in their CNS so that the channels have difficulty binding to GABA and do not open as quickly to normal levels of GABA, what is the result? •

The persons CNS neurons are likely to more positive (excited) compared to normally functioning neurons!

Many common sedative drugs (ambien, valium) bind to the same channel and ENHANCE the effect of GABA binding to the channel steps •

Resting state! ◦

Voltage gated Na+ and K+ channels (in axon) are closed!

1. Local potential reaches threshold (-55mV)! 1. Excitation causes potential at axon hillock to become more positive! 2. When potential passes threshold, neuron “fires” or starts an !

2. Voltage gated sodium channels open in axon! 1. Channels only open when threshold potential is reached! 2. Sodium diffuses into the cytoplasm! 3. Membrane depolarizes, becomes less negative! 3. Membrane potential reaches +30mV! 1. This is peak depolarization! 2. Sodium channels close! 3. Potassium voltage gated channels open! 4. Potassium diffuses out of the cell! 5. Cell begins to repolarize (become more negative)! 4. Potassium channels stay open longs! 1. More potassium leaves the cell than sodium enters! 2. HYPERPOLARIZATION! 3. K+ channels close and sodium/potassium pumps actively transport ions back to original state!

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